Chromium-Aluminum Binary Alloy Having Excellent Corrosion Resistance and Method of Manufacturing Thereof

ABSTRACT

The present disclosure relates to a chromium-aluminum binary alloy with excellent corrosion resistance and a method of producing the same, and more particularly to a chromium-aluminum binary alloy with excellent corrosion resistance, including: 1 to 40% by weight of aluminum (Al), the balance of chromium (Cr), and other unavoidable impurities with respect to a total weight of the alloy, and a method of producing a chromium-aluminum binary alloy with excellent corrosion resistance, the method including: (Step  1 ) mixing and melting a raw material comprising: 1 to 40% by weight of aluminum (Al), the balance of chromium (Cr), and other unavoidable impurities with respect to a total weight of the alloy; and (Step  2 ) solution treating the alloy melted in Step  1.  The chromium-aluminum binary alloy may be easily produced and has ductility, thus being highly applicable as a coating material for a material requiring high-temperature corrosion resistance and wear resistance.

CROSS-REFERENCES TO RELATED APPLICATION

This patent application claims the benefit of priority from KoreanPatent Application No. 10-2014-0141522, filed on Oct. 20, 2014, thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a chromium-aluminum binary alloy withexcellent corrosion resistance and a method of producing the same, andmore particularly, to a chromium-aluminum binary alloy including 1 to40% by weight of aluminum and to a method of producing the same.

2. Description of the Related Art

A zirconium alloy material used as a core component of a fuel assemblyin Japan's Fukushima accident generated a large amount of hydrogen by avery high corrosion reaction rate to act as the cause of a hydrogenexplosion in a high-temperature oxidizing atmosphere in which coolantwas lost and a temperature of a nuclear fuel was increased.

From this fact, it was confirmed that when the current zirconium alloymaterial was used as a core material of a nuclear power plant, there wasno big problem in a steady-state, but safety was not guaranteed in anaccident-state.

One of ways to overcome the limitation of the zirconium alloy at ahigh-temperature accident-state and to greatly enhance safety of thefuel assembly is to replace the zirconium alloy with a material havingan excellent oxidation resistance or to coat a zirconium alloy surfacewith an oxidation-resistant material to increase oxidation resistance.

That is, when a material in which oxidation is hardly generated isapplied to the zirconium alloy or an oxidation-resistant coatingmaterial stable at a high-temperature environment of an accident-stateis present on a zirconium alloy surface, an oxidation reaction issignificantly suppressed to reduce hydrogen generation by the oxidationreaction, so that a risk of hydrogen explosion may be blocked.

To solve this problem, in laboratories and academia worldwide, researchfor developing a SiC/SiC_(f) material, a FeCrAl alloy, a Zr—Mo-coatedcladding tube, a Zr-coated cladding tube or the like with a new materialhas been in progress to improve safety of a nuclear power plant in anenvironment such as the Fukushima accident.

However, these material technologies are favorable in a normal-state butunfavorable in an accident-state, and vise versa. For example, aSiC/SiC_(f) material is being evaluated to have excellenthigh-temperature strength and superior oxidation resistance, but to havedrawbacks in that the material dissolution very quickly in asteady-state ambient and the production cost is very high.

The FeCrAl alloy has excellent corrosion resistance under steady andaccident-states, but, due to a material characteristic, has a largeneutron absorption cross-sectional area and a low tritium collectionproperty, thus having a disadvantage in that the FeCrAl alloy iseconomically infeasible when being used in a steady operation.

The Zr—Mo-coated cladding tube is excellent in high temperaturestrength, but greatly increases a cost for producing the cladding as atrilayer and still has a lot of problems to be technically solved.

The Zr-coated cladding tube has an advantage of accelerating adevelopment cycle with a relatively low cost compared to othertechnologies, but has a problem of a low coating effect due to a peelingproblem of a coating layer and a reaction of a coating material with aZr-base material at a high temperature.

That is, when the FeCrAl alloy with excellent corrosion resistance isapplied to the Zr-coated cladding tube, there are problems in which acomposition of the coating material is changed by interdiffusion of Zrand Fe at a temperature of 950° C. or higher and a base material of theZr cladding tube form a Zr—Fe-based intermetallic compound to beweakened.

When a pure Cr layer is applied to the base material of the Zr claddinglayer, interdiffusion between Cr and Zr may take place at 1400° C. orhigher to reduce a problem due to a microstructure change. However, theZr-coated cladding tube is weak to an impact due to low ductility of theCr layer and has a relatively low high-temperature oxidation resistancecompared to the FeCrAl alloy.

Meanwhile, as a related art regarding high a corrosion resistance alloy,Korea Patent Registration No. 10-0584113 discloses an FeCrAl materialand a method of producing the same. Specifically, as a method ofproducing an FeCrAl material by gas atomization, the related artprovides a method of producing an FeCrAl material, the method beingcharacterized in that the FeCrAl material contains: iron (Fe), chromium(Cr), and aluminum (Al) and further includes at least one of molybdenum(Mo), hafnium (Hf), zirconium (Zr), yttrium (Y), nitrogen (N), carbon(C), and oxygen (O); a smelt to be sprayed contains 0.05% to 0.50% byweight of tantalum (Ta) and titanium (Ti)less than 0.10% by weight; anda composition of the smelt is determined such that a composition of apowder obtained after the spraying becomes Fe: balance, Cr: 15-25, Al:3-7, Mo: <5, Y: 0.05-0.60, Zr: 0.01-0.30, Hf: 0.05-0.50, Ta: 0.05-0.50,Ti: <0.10, C: 0.01-0.05, N: 0.01-0.06, O: 0.02-0.10, Si: 0.10-0.70, Mn:0.05-0.50, P: <0.8, S: <0.005 [unit of % by weight].

However, since the FeCrAl material, due to a material characteristicthereof, has a large neutron absorption cross-sectional area and a lowcollection property of tritium generated in a nuclear fuel, the FeCrAlmaterial is economically infeasible used in a steady operation, and hasa problem in which a base material of the Zr cladding tube forms aZr—Fe-based intermetallic compound to be weakened when the FeCrAlmaterial is applied to the Zr cladding tube.

Thus, it is difficult to realize both safety and economic feasibilitywith a combination of materials and coating technologies reported sofar, under a steady-state or an accident-state of nuclear power.

Therefore, while carrying out a research about a material having highcorrosion resistance, the material being able to realize both safety andeconomic feasibility under a steady-state or an accident-state ofnuclear power, the present inventors confirmed that a chromium-aluminumbinary alloy including 1 to 40% by weigh of aluminum has high hardnessand good oxidation resistance, and completed the present invention.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a chromium-aluminumbinary alloy with excellent corrosion resistance.

Another object of the present invention is to provide a method ofproducing a chromium-aluminum binary alloy with excellent corrosionresistance.

Still another object of the present invention is to provide ahigh-temperature environment structural material including achromium-aluminum binary alloy with excellent corrosion resistance.

Even another object of the present invention is to provide a surfacecoating material of a metal material, the surface coating materialincluding a chromium-aluminum binary alloy with excellent corrosionresistance.

In order to achieve the objects, the present invention provides achromium-aluminum binary alloy with excellent corrosion resistance, thechromium-aluminum binary alloy including 1 to 40% by weight of aluminum,the balance of chromium (Cr), and other unavoidable impurities withrespect to a total weight of the alloy.

The present invention also provides a producing method of achromium-aluminum binary alloy with excellent corrosion resistance, theproducing method including: mixing and melting a raw material including1 to 40% by weight of aluminum (Al), the balance of chromium (Cr), andother unavoidable impurities with respect to a total weight of the alloy(Step 1); and solution treating the alloy melted during Step 1 (Step 2).

Furthermore, the present invention provides a chromium-aluminum binaryalloy with excellent corrosion resistance, which is produced accordingto the method and has hardness of 250 to 450 Hv, and high-temperatureoxidation resistance is 100 to 200 times higher than that of azircaloy-4 alloy, 5 to 10 times higher than that of pure chromium, and 2to 10 times higher than that of an FeCrAl alloy.

Furthermore, the present invention provides a high-temperatureenvironment structural material including the chromium-aluminum binaryalloy with excellent corrosion resistance.

Furthermore, the present invention provides a surface coating materialof a metal material, the surface coating material including thechromium-aluminum binary alloy with excellent corrosion resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a graph showing hardness of a chromium-aluminum binary alloyproduced in Examples 1 to 5 and a metal material of Comparative Examples1 to 3 measured by a micro Vickers hardness tester;

FIG. 2 shows a photograph of a high-temperature oxidation experimentapparatus and a schematic diagram of an experimental condition;

FIG. 3 is a graph showing an increase in weight as a function of time ofchromium-aluminum binary alloys produced in Examples 1 to 5 and metalmaterials of Comparative Examples 1 to 3 due to a high-temperatureoxidation experiment;

FIG. 4 is a graph showing an increase in weight of chromium-aluminumbinary alloys produced in Examples 1 to 5 and metal materials ofComparative Examples 1 to 3 after a high-temperature oxidationexperiment for 7200 seconds;

FIG. 5 is a semi-log graph converted from the graph of FIG. 4; and

FIG. 6 shows photographs of cross-sections of chromium-aluminum binaryalloys produced in Examples 1 to 5 and metal materials of ComparativeExamples 1 to 3 as observed by a scanning electron microscope after ahigh-temperature oxidation experiment.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a chromium-aluminum binary alloy withexcellent corrosion resistance, the chromium-aluminum binary alloyincluding 1 to 40% by weight of aluminum, the balance of chromium, andother unavoidable impurities with respect to a total weight of thealloy.

Hereinafter, the chromium-aluminum binary alloy with excellent corrosionresistance according to the present invention will be described in moredetail.

Conventionally, in order to improve safety of a nuclear power plant, aSiC/SiC_(f) material, a FeCrAl alloy, a Zr—Mo-coated cladding tube, aZr-coated cladding tube and the like have been developed as advancedmaterials, but have drawbacks as described above.

Accordingly, combinations of materials and coating technologies reportedso far have a difficulty in realizing both safety and economicfeasibility in a steady-state and an accident-state of nuclear power.

However, the present invention provides a chromium-aluminum binary alloyin which a content of aluminum is 1 to 40% by weight with respect to atotal weight of the alloy.

Cr forms a stable oxide of Cr₂O₃ by an oxidation reaction and Al forms astable oxide Al₂O₃ by an oxidation reaction, thus increasing corrosionresistance of the Cr—Al binary alloy. When applied to nuclear power, thechromium-aluminum binary alloy has excellent corrosion resistance in anaccident-state as well as a steady-state operation, thus providingeffects of being able to significantly increase economic feasibility andaccident safety of nuclear power.

When a binary alloy includes less than 1% by weight of aluminum, thereis a problem in that improvement in corrosion resistance due to aluminumis slight, and when a binary alloy includes more than 40% by weight ofaluminum, the binary alloy has low corrosion resistance due togeneration of an Al₈Cr₅ intermetallic compound, is lack ofprocessability because the intermetallic compound has very highbrittleness on characteristic, and has a difficulty in controlling thecomposition thereof. In addition, since a melting point decreases as anadded amount of aluminum increases, there is a problem in that itbecomes impossible to use the binary alloy at high temperatures, such asa nuclear power plant accident environment.

The aluminum is preferable included in an amount of 1% to 18% by weightor 22% to 40% by weight.

When 1% to 18% by weight of aluminum is included, the aluminum ispresent as a solute in the Al—Cr solid solution, and when 22% to 40% byweight of aluminum is included, an aluminum-rich phase and achromium-rich phase are present in a separate state in the alloy.

When more than 18% and less than 22% by weight of aluminum is included,an AlCr₂ intermetallic compound may be generated to rather reducecorrosion resistance.

The present invention provides a method of producing a chromium-aluminumbinary alloy with excellent corrosion resistance, the method including:mixing and melting raw materials including 1 to 40% by weight ofaluminum (Al), the balance of chromium (Cr), and other unavoidableimpurities with respect to a total weight of the alloy (Step 1); andsolution treating the alloy melted during Step 1 (Step 2).

Hereinafter, a method of producing a chromium-aluminum binary alloy withexcellent corrosion resistance according to the present invention willbe described for each step in more detail.

In the method of producing a chromium-aluminum binary alloy withexcellent corrosion resistance according to the present invention, Step1 is a step of mixing and melting raw materials including 1 to 40% byweight of aluminum (Al), the balance of chromium (Cr), and otherunavoidable impurities with respect to a total weight of the alloy.

In Step 1, the raw materials are mixed and melted in a molten metal bathto produce an alloy in which the raw materials are homogeneously mixed.

Conventionally, in order to improve safety of a nuclear power plant, aSiC/SiC_(f) material, a FeCrAl alloy, a Zr—Mo-coated cladding tube, aZr-coated cladding tube and the like have been developed as advancedmaterials, but have drawbacks as described above. Accordingly,combinations of materials and coating technologies reported so far havea difficulty in realizing both safety and economic feasibility in asteady-state and an accident-state of nuclear power.

However, the present invention provides a chromium-aluminum binary alloyin which an amount of aluminum is 1% to 40% by weight.

Compared to oxide-based (SiO₂, Cr₂O₃, Al₂O₃, ZrO₂), carbide-based(Cr₃C₂, SiC, ZrC), nitride-based (ZrN) intermetallic compounds, and aMAX phase (C or N-added compound), the chromium-aluminum binary alloy iseasy to produce. Also, the ductility of the chromium-aluminum binaryalloy not only makes it easy to produce a product but also improvesapplicability as a coating material. In addition, the chromium-aluminumbinary alloy has excellent corrosion resistance to significantly reducea hydrogen explosion phenomenon caused by an excessive oxidationreaction when used as a component and a coating material of a nuclearpower plant.

The aluminum is preferably included in an amount of 1% to 18% by weightor 22% to 40% by weight. When 1% to 18% by weight of aluminum isincluded, the aluminum is present as a solute in the Al—Cr solidsolution, and when 22% to 40% by weight of aluminum is included, analuminum-rich phase and a chromium-rich phase are present in a separatestate in the alloy. When more than 18% and less than 22% by weight ofaluminum is included, an AlCr₂ intermetallic compound may be generatedto rather reduce corrosion resistance.

Meanwhile, the melting in Step 1 may be performed at a temperature of1400° C. to 1800° C. When the melting of Step 1 is performed less than1400° C., there may be a problem in which a liquid molten state is notmaintained and thus an alloy is not properly formed, and when themelting of Step 1 is performed more than 1800° C., there may be causedproblems in which reactivity of molten metal is increased to include alarge amount of impurities, and Al having a low melting point isevaporated to have a difficulty in controlling the composition, andcosts increase.

In the method of producing a chromium-aluminum binary alloy withexcellent corrosion resistance according to the present invention, Step2 is a step of solution treating the alloy melted during Step 1.

In Step 2, the alloy melted in Step 1 is heated up to a range in whichthe melted alloy becomes a solid solution, and is quenched to maintainthe solid solution state, and through this step, the alloy elements mayreadily form the solid solution.

The solution treating of Step 2 may be performed at a temperature of950° C. to 1200° C. When the temperature is lower than 950° C. in thesolution treating of Step 2, there is a problem in which the precipitateAlCr₂ is not completely melted and thus a desired property is notobtained, and when the temperature is higher than 1200° C., a productioncost is increased so that the solution treating of Step 2 iseconomically infeasible.

The present invention provides a chromium-aluminum binary alloy withexcellent corrosion resistance, the chromium-aluminum binary alloy whichis produced according to the above-described method, and has hardness of250 to 450 Hv, and high-temperature oxidation resistance 100 to 200times higher than that of a zircaloy-4 alloy, 5 to 10 times higher thanthat of pure chromium, and 2 to 10 times higher than that of an FeCrAlalloy.

The present invention relates to a chromium-aluminum binary alloyincluding 1 to 40% by weight of aluminum, the binary alloy being able tohave excellent mechanical property and corrosion resistance at roomtemperature as well as at high temperatures. In particular, thechromium-aluminum binary alloy may have hardness of 250 to 450 Hv, andhigh-temperature oxidation resistance 100 to 200 times higher than thatof a zircaloy-4 alloy, 5 to 10 times higher than that of pure chromium,and 2 to 10 times higher than that of a FeCrAl alloy.

The present invention provides a high-temperature environment structuralmaterial including the chromium-aluminum binary alloy with excellentcorrosion resistance.

Since the chromium-aluminum binary alloy according to the presentinvention has excellent corrosion resistance even at high temperature aswell as at room temperatures, the chromium-aluminum binary alloy may benot only used as a material for components of a nuclear power plant butalso be applied to a structural material used in a high temperatureenvironment, such as thermal power generation and an aircraft engine,and a gas turbine.

The present invention provides a surface coating material including thechromium-aluminum binary alloy with excellent corrosion resistance.

According to the present invention, since the chromium-aluminum binaryalloy has superior corrosion resistance, is easy to produce, and hasductility, the chromium-aluminum binary alloy may be applied as acoating material.

The chromium-aluminum binary alloy may be utilized as a zirconiumcoating material used in a nuclear power plant, and as a coatingmaterial of a metal structural material used at a high temperature inaddition to the nuclear power plant.

In the case, the metal material may be stainless steel or inconel andhas advantages of reducing a cost and a term for technology developmentcompared to an advanced anti-oxidation material, by coating the alloy ofthe present invention on such a metal material.

Hereinafter, the present invention will be described below in detailwith reference to the following examples. However, the followingexamples are provided for illustrative purposes only, and the scope ofthe present invention should not be limited thereto in any manner.

EXAMPLE 1 Production of a Cr-2Al Alloy

Step 1: a melting temperature was set to 1600° C., and through a vacuumarc melting, an alloy having a composition including 2% by weight ofaluminum, the balance of chromium and other unavoidable impurities wasproduced.

Step 2: the alloy undergone Step 1 was solution treated at 1100° C. for20 minutes to produce a chromium-aluminum binary alloy.

EXAMPLE 2 Production of a Cr-4Al Alloy

In step 1 of Example 1, except that the amount of aluminum was changedto 4% by weight, a chromium-aluminum binary alloy was produced byperforming the same procedure as Example 1.

EXAMPLE 3 Production of a Cr-6Al Alloy

In step 1 of Example 1, except that the amount of aluminum was changedto 6% by weight, a chromium-aluminum binary alloy was produced byperforming the same procedure as Example 1.

EXAMPLE 4 Production of a Cr-15Al Alloy

In step 1 of Example 1, except that the amount of aluminum was changedto 15% by weight, a chromium-aluminum binary alloy was produced byperforming the same procedure as Example 1.

EXAMPLE 5 Production of a Cr-30Al Alloy

In step 1 of Example 1, except that the amount of aluminum was changedto 30% by weight, a chromium-aluminum binary alloy was produced byperforming the same procedure as Example 1.

COMPARATIVE EXAMPLE 1 Pure Chromium

A commercial high purity chromium for a coating raw material (purity of99.9% or more) was prepared as Comparative Example 1.

COMPARATIVE EXAMPLE 2 FeCrAl

A commercial FeCrAl alloy (product name: Kantal APMT) was prepared asComparative Example 2.

COMPARATIVE EXAMPLE 3 Zircaloy-4

A commercial zircaloy-4 (product name: zircaloy-4) was prepared asComparative Example 3.

EXPERIMENTAL EXAMPLE 1 Hardness Measurement

To investigate a mechanical property of the chromium-aluminum alloysproduced in Examples 1 to 5 and metal materials of Comparative Examples1 to 3, hardness was measured in a condition of maintaining a load of 98mN for 10 seconds at room temperature by a micro Vickers hardness testerand the result is shown in FIG. 1. At this time, the hardness value wasmeasured 10 times for each sample and an average was taken.

As shown in FIG. 1, it can be seen that Examples 1 to 5 have a highhardness of about 260 to 410 Hv. On the other hand, the pure chromium inComparative Example 1 had hardness of about 290 Hv, and the FeCrAl-alloyin Comparative Example 2 had hardness of about 260 Hv, and thezircaloy-4 in Comparative Example 3 had hardness of about 240 Hv, but itcan be seen that hardness of these Comparative Examples does not exceedabout 300 Hv.

As a result of observing indentation after the hardness measurement,since a hardness value was high, but a crack around the indentation wasnot observed in the alloys of Examples of the present invention, it wasconfirmed that there is no brittleness appearing in an oxide materialand an intermetallic compound.

From these results, it can be seen that the hardness of thechromium-aluminum binary alloys according to the present invention isexcellent compared to that of the metal materials of ComparativeExamples. In addition, since the alloys of Examples of the presentinvention have higher hardness than zircaloy-4, the alloys of Examplesof the present invention will have high wear resistance compared tozircaloy-4 when applied to a cladding tube.

EXPERIMENTAL EXAMPLE 2 High-Temperature Oxidation Resistance Measurement

To investigate high-temperature oxidation resistance of thechromium-aluminum alloys produced in Examples 1 to 5 and metal materialsof Comparative Examples 1 to 3, a temperature was raised to 1200° C. ata heating rate of 50° C./min and was maintained for 7200 seconds, andair-cooled to perform an experiment on high temperature steam oxidationwith a thermogravimetric analyzer (TGA-51-SHIMADZU) shown in FIG. 2, andthe result is shown in FIGS. 3 to 5. In addition, after the experimenton the high temperature steam oxidation, cross-sections of Example 3 to5 were observed by a scanning electron microscope and the results areshown in FIG. 6.

As shown in FIGS. 3 to 5, it can be seen that an oxidation amount ofExamples 1 to 5 is at least about 20 times less than, at most about 200times less than that of the zirconium alloy of Comparative Example 3. Inparticular, in the case of Example 1 to 3 and 5, it can be seen that anoxidation amount of Examples 1 to 5 is at least about 10 times less thanpure chromium of Comparative Example 1 and a FeCrAl alloy of ComparativeExample 2.

As shown in FIG. 6, in the case of Examples 1 to 3 and 5 in which hightemperature oxidation resistance characteristics are most excellent, itcan be seen that a dense oxide film without a crack was formed on asurface of each of the alloys.

From these results, it can be seen that high-temperature oxidationresistance of the chromium-aluminum binary alloy including 1 to 40% byweight of aluminum is excellent compared to zirconium, pure chromium, anFeCrAl Alloy, and in particular, in the cases of including 1 to 12% or20 to 40% by weight of aluminum, a more excellent oxidation resistanceproperty is exhibited.

According to the present invention, a chromium-aluminum binary alloy iseasy to produce and has ductility, thus being highly applicable to amaterial requiring high-temperature corrosion resistance and wearresistance, as a coating material. In addition, the chromium-aluminumbinary alloy has excellent corrosion resistance in an accident-state ofnuclear power as well as a steady-state operation, thus providingeffects capable of significantly increasing economic feasibility andaccident safety of nuclear power.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

What is claimed is:
 1. A chromium-aluminum binary alloy with excellentcorrosion resistance, comprising: 1 to 40% by weight of aluminum (Al),the balance of chromium (Cr), and other unavoidable impurities withrespect to a total weight of the alloy.
 2. The chromium-aluminum binaryalloy of claim 1, wherein the aluminum is contained in an amount of 1 to18% by weight or 22 to 40% by weight with respect to the total weight ofthe alloy.
 3. A method of producing a chromium-aluminum binary alloywith excellent corrosion resistance, the method comprising: (Step 1)mixing and melting a raw material comprising: 1 to 40% by weight ofaluminum (Al), the balance of chromium (Cr), and other unavoidableimpurities with respect to a total weight of the alloy; and (Step 2)solution treating the alloy melted in Step
 1. 4. The method of claim 3,wherein the aluminum is contained in an amount of 1 to 18% by weight or22 to 40% by weight with respect to the total weight of the alloy. 5.The method of claim 3, wherein the melting of Step 1 is performed at atemperature of 1400° C. to 1800° C.
 6. The method of claim 3, whereinthe solution treating of Step 2 is performed at a temperature of 950° C.to 1200° C.
 7. A chromium-aluminum binary alloy with excellent corrosionresistance, produced according to the method of claim 3, thechromium-aluminum binary alloy having a hardness of 250-450 Hv, andhigh-temperature oxidation resistance 100 to 200 times higher than thatof a zircaloy-4 alloy, 5 to 10 times higher than that of pure chromium,and 2 to 10 times higher than that of an FeCrAl alloy.
 8. Ahigh-temperature environment structural material comprising thechromium-aluminum binary alloy with excellent corrosion resistance ofclaim
 7. 9. A surface coating material for a metal material, comprisingthe chromium-aluminum binary alloy with excellent corrosion resistanceof claim
 7. 10. The surface coating material of claim 9, wherein themetal material is stainless steel or inconel.